Google releases a day-one patch for the Pixel 6 and Pixel 6 Pro
Google and retailers have started shipping the Pixel 6 and Pixel 6 Pro following a particularly protracted teaser period. As predicted by Mishaal Rahman, Google has issued a day-one update for the pair, which it is distributing as SD1A.210817.036, appended with '.A8' if you bought the Pixel 6 or Pixel 6 Pro through Verizon.
Unfortunately, Google has not explained what it has added with SD1A.210817.036. However, in a blog post, it writes that the update brings all advertised features to the Pixel 6 series. Hence, it seems that SD1A.210817.036 is the Pixel 6 series' release software, with everything else being pre-release builds.
As usual, you can download SD1A.210817.036 from within Settings under System/System update. Google states that the update will take between 25 and 50 minutes to finish depending on your network speed. The Pixel 6 and Pixel 6 Pro should receive a notification to download SD1A.210817.036. If that is not the case, you can manually trigger it by selecting 'Check for update' once you have navigated to the 'System update' sub-menu.
Additionally, SD1A.210817.036 contains the November 2021 security patch. Incidentally, Google also recommends updating your apps in the Play Store after installing SD1A.210817.036, as many have received Pixel 6-specific improvements and features.